1. Field of Invention
This invention is directed to semiconductor light-emitting devices. More particularly, this invention is directed to semiconductor light-emitting devices that include polycrystalline GaN.
2. Description of Related Art
Group-III nitrides include elements from group III of the periodic table, i.e., Al, Ga and In. These materials are deposited over substrates to form layered structures for optoelectronic devices. The devices can emit visible light over a wide range of wavelengths. GaN and its alloys with InN and AlN can be used in visible light-emitting devices that produce high emission efficiencies. Crystalline heterostructures of these materials are typically deposited epitaxially on single-crystal substrates by vapor phase epitaxy techniques. For example, full-color outdoor displays can be formed by combining existing red emitters and blue and green InGaN/AlGaN light-emitting diodes (LEDs).
LEDs have been produced that can emit all three primary colors (red, green, blue). These devices have potential utility for large-area displays. By mixing two or more colors, a range of intermediate colors can potentially be produced in such displays.
Single crystal group III-nitride LEDs have a high emission efficiency despite having high defect concentrations. These materials can have dislocation densities of.about.10.sup.10 cm.sup.-2. These extended defects apparently do not influence carrier flow and recombination in devices that are fabricated from these materials. This insensitivity is surprising in light of the known adverse effects that extended (i.e., one and two-dimensional) lattice defects, such as dislocations and stacking faults, normally have on the optoelectronic properties of semiconducting materials.